The present invention generally relates to a motor driving device, a motor driving method, and an electronic device having the motor driving device.
A brushless motor driving device detects a rotor position of a motor to be controlled, and sends a current to a stator winding according to the position signal. However, the phase of the position signal is sometimes shifted due to various factors, such as rotation number and load torque of the motor. Thereby, the electrification phase is shifted, the driving efficiency of the motor becomes low, and the power consumption increases. Moreover, when the motor is driven with the voltage having a rectangular waveform based on rotor position information which is obtained a few times per one rotation of motor, the motor vibrates and noise is generated during the rotation of the motor.
Japanese Unexamined Patent Publication 2001-037279 discloses motor driving devices of the first and second prior arts. Referring to FIGS. 14 and 15, the motor driving devices of the first and second prior arts are explained. FIGS. 14 and 15 show block diagrams of the motor driving devices of the first and second prior arts, respectively.
The motor driving device of the first prior art shown in FIG. 14 will be explained. In FIG. 14, a DC power source 1 provides power to the motor driving device. A current detector 4 detects the source current flowing in a motor driving part 2. A rotor position detector 13 outputs a position signal having a certain phase relation with a voltage induced in the stator winding of a plurality of phases according to the rotor rotating position of a permanent-magnet motor 3. A cycle measuring part 1401 measures a variable cycle of the position signal. A pulse generator 1402 generates a plurality of clock pulses in the variable cycle.
A peak hold part 1408 holds a peak value of the signal detected by the current detector 4. A rotation number detector 1405 counts the rotation number of the permanent-magnet motor 3, for example by counting the number of output rising edges per second with respect to one of the position signals. The rotation number detector 1405 then outputs the voltage signal Vf having a level according to the rotation number to an adder 1409 to execute F/V conversion. The adder 1409 adds the voltage signal levels output by the rotation number detector 1405 and the peak hold part 1408 in an analog manner. An A/D converter 1409 converts an analog voltage signal given from the adder 1409 to digital information, and outputs the digital information.
A phase estimating part 1403 has a counter for counting the number of the generated clock pulses, and estimates the rotor phase based on a counter value of the counter using the timing in which the position signal changes as a reference. A phase correcting part 1407 sets the correction value derived based on the output signal of the A/D converter 1406 to the counter at the timing when the position signal changes so as to correct the rotor phase. Particularly, the phase correcting part 1407 corrects the phase depending on, for example, the increase in the load torque of the motor 3 so that the commutation timing at the stator winding is advanced. A voltage signal generator 1404 generates a predetermined voltage signal depending on the rotor phase. A triangular wave generator 8 generates a triangular wave to generate a carrier wave of a pulse width modulation (PWM) signal. A driving signal generator 9 compares the signal level of the voltage signal to that of the carrier wave, to generate a driving signal. The motor driving part 2 sends a current to the stator winding of a plurality of phases according to the driving signal.
The motor driving device of the first prior art sends a current to each stator winding of the motor 3 according to torque current information output from the current detector 4, and rotation number information and phase information output from the rotor position detector 13.
The motor driving device of the second prior art shown in FIG. 15 will be explained below. The motor driving device of the second prior art has the configuration similar to that of the motor driving device of the first prior art. In FIG. 15, the same reference numerals denote the components that are similar or equal to in the first prior art, and the description thereof is omitted. The parts differing from the first prior art will be described below.
As shown in FIG. 15, the motor driving device of the second prior art does not have the adder 1409, the current detector 4 and the peak hold part 1408 apart from the configuration of the first prior art, but has a speed controller 1501 and a phase controller 1502. The speed controller 1501 compares the speed command given from outside with the rotation number detected by the rotation number detector 1405, and outputs the voltage command depending on that difference. The phase controller 1502 differential-amplifies the difference between the voltage command and the voltage signal Vf that is input from the rotation number detector 1405, to generate a phase command. Then the phase correcting part 1407 uses the digital data obtained by A/D-converting the phase command as a phase correction value PC.
The motor driving device of the second prior art sends a current to the stator winding according to the speed command that is input from outside, and the rotation number information and the phase information from the rotor position detector 13.
The motor driving devices of the first and second prior arts estimate the rotor phase according to the counter value of the counter. Thereby, the motor driving devices of the first and second prior arts obtain the rotor phase with higher resolution than the variable cycle, and drive the motor 3 with sine-wave voltage based on the detailed rotor phase information. In such a way, the motor driving devices of the first and second prior arts can reduce vibration and noise etc. generated from the motor, and can drive the motor with high efficiency.
In the motor driving devices of the first and second prior arts, the phase difference between the induced voltage of each phase and the phase information from the rotor position detector 13 is determined from a characteristic of each motor. The phase of the voltage to be applied to each stator winding is a predetermined value depending on the rotation number of the motor.
The motor driving devices of the prior art control the phase according to the predetermined value that is determined by the characteristic of each motor independently. Therefore, the predetermined value needs to be determined depending on electrical constants of resistance and inductance of the motor. In the motor driving devices controlling the motor with microcomputers, it is easy to change these predetermined values. The motor driving devices for the devices having an expensive and large-sized motor, such as washing machines and air-conditioners, control the phase with high accuracy in usage of the microcomputers. However, the motor driving devices for controlling relatively small-sized motor are required to be low in cost and high in versatility that is not depending on the structure and/or the characteristic of the motor.
The motor driving devices of the first and second prior arts have not realized the motor driving devices that are low in cost and high in versatility. The quantity of the phase correction varied by the rotation number and the load torque of the motor depends on the characteristic of each motor. The motor driving devices of the first and second prior arts are configured to drive a certain type of the motor. Therefore, the motor driving devices of the first and second prior arts can not execute the optimum phase correction in the case that the motor driving devices drive the motor having different electrical constants (e.g. resistance or inductance etc.) from the certain type of the motor.
The present invention is intended to provide a motor driving device and a motor driving method that are low in cost and can control the phase of the motor with high efficiency and high accuracy.
The present invention is intended to provide a motor driving device and a motor driving method that are low in cost and can control the phase of the motor with high efficiency and high accuracy without depending on the characteristic of the motor.
The present invention is intended to provide an electronic device that is low in cost and high in efficiency.